Introduction
Regular expression patterns are often used with modifiers (also called flags) that redefine regex behavior. Regex modifiers can be regular (e.g. /abc/i) and inline (or embedded) (e.g. (?i)abc). The most common modifiers are global, case-insensitive, multiline and dotall modifiers. However, regex flavors differ in the number of supported regex modifiers and their types.
PCRE Modifiers
| Modifier | Inline | Description |
|---|
| PCRE_CASELESS | (?i) | Case insensitive match |
| PCRE_MULTILINE | (?m) | Multiple line matching |
| PCRE_DOTALL | (?s) | . matches new lines |
| PCRE_ANCHORED | (?A) | Meta-character ^ matches only at the start |
| PCRE_EXTENDED | (?x) | White-spaces are ignored |
| PCRE_DOLLAR_ENDONLY | n/a | Meta-character $ matches only at the end |
| PCRE_EXTRA | (?X) | Strict escape parsing |
| PCRE_UTF8 | | Handles UTF-8 characters |
| PCRE_UTF16 | | Handles UTF-16 characters |
| PCRE_UTF32 | | Handles UTF-32 characters |
| PCRE_UNGREEDY | (?U) | Sets the engine to lazy matching |
| PCRE_NO_AUTO_CAPTURE | (?:) | Disables auto-capturing groups |
Java Modifiers
Modifier (Pattern.###) | Value | Description |
|---|
| UNIX_LINES | 1 | Enables Unix lines mode. |
| CASE_INSENSITIVE | 2 | Enables case-insensitive matching. |
| COMMENTS | 4 | Permits whitespace and comments in a pattern. |
| MULTILINE | 8 | Enables multiline mode. |
| LITERAL | 16 | Enables literal parsing of the pattern. |
| DOTALL | 32 | Enables dotall mode. |
| UNICODE_CASE | 64 | Enables Unicode-aware case folding. |
| CANON_EQ | 128 | Enables canonical equivalence. |
| UNICODE_CHARACTER_CLASS | 256 | Enables the Unicode version of Predefined character classes and POSIX character classes. |
